Amplitude stabilizer for timepiece

ABSTRACT

A CONSTANT AMPLITUDE MAGNETICALLY DRIVEN MECHANICAL TIMEPIECE OSCILLATOR HAVING ADRIVE COIL CONNECTED O A DC SOURCE THROUGH THE EMITTER-COLLECTOR LINE OF A TRANSISTOR CURRENT IN THE COIL DURING DRIVE IS LIMITED BY HAVING BASE POTENTIAL DEPENDENT ON VOLTAGE ACROSS THE COIL, POTENTIAL BEING APPLIED THROUGH A DIODE.

1971 s. HILS 3,561,208

AMPLITUDE STABILIZER FOR :rmmxzcz Filed Aug. 19, 1968 INVENTOR SIEGBLRT HILS y Attorney United States Patent Olfice U.S. Cl. 5823 3 Claims ABSTRACT OF THE DISCLOSURE A constant amplitude magnetically driven mechanical timepiece oscillator having a drive coil connected to a DC source through the emitter-collector line of a transistor. Current in the coil during drive is limited by having base potential dependent on voltage across the coil, potential being applied through a diode.

RELATED APPLICATION My application Ser. No. 645,223 filed June 12, 1967.

BACKGROUND OF THE INVENTION (1) Field of the invention Magnetically driven mechanical oscillator having means for limiting amplitude or speed, of oscillator.

(2) Description of the prior art In general controls of this kind employ a mechanical oscillator having a permanent magnet thereon swing past a drive coil and a control coil.

It has been proposed to use a first induction coil to charge a resistor-shunted condenser through a diode with a resistor, the condenser and resistor lying in the emittercollector line of a drive transistor. In this circuit a voltage is impressed on the condenser preventing modulation of the transistor and this voltage is dependent on the amplitude of the oscillatory system. The voltage is counter to the voltage induced by a control coil cooperating with a moving magnet mounted on a part of the oscillatory system and in the base-emitter circuit of the transistor. The main drawback with this circuit is that it requires a large number of component parts, for in order to get the necessary charge on the condenser a feedback transformer is required.

There have been various circuits proposed wherein transistors are used with drive and control coils but they do not limit amplitude, except by wasteful dissipation of energy such as supplied by a battery.

The present invention overcomes essentially all of the energy waste and reduces the number of parts.

SUMMARY OF THE INVENTION In a timepiece mechanical oscillator wherein a permanent magnet cooperates with a drive coil energized by DC through a drive transistor, there is serially connected with the source of DC a limiting resistor. In this serial circuit a second transistor functions as the limiting, or as a variable, resistor for maintaining a substantially constant flow of current through the coil whenever the drive transistor is conductive. The second transistor is biased by a potential derived from a high resistance shunted around the second transistor and coil the shunt being provided with a one-way diode to insure proper polarity to the base of the second transistor. The shunt need not cover the entire drive coil.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 shows the circuitry wherein the second transistor is of the n-p-n type;

3,561,208 Patented Feb. 9, 1971 FIG. 2 shows connection for transistor of the p-n-p type, and

FIG. 3 shows the mechanical oscillator.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In FIG. 1 assuming transistor 2 conductive and considering first the positive side of the network, the transistor 1 is modulated in known manner by a fixed control or pick-up coil 3', the coil being inductively acted upon by a permanent magnet M mounted to move with a mechanically oscillatory member S. Upon a corresponding directional controller impulse the emitter collector line of drive transistor 1 is made conductive with the result that current flows through a drive coil 4, assuming transistor 2 to be conductive. A capacitor 8 in the base-emitter circuit, and a resistor 7 giving proper bias to the base of the transistor 1, both well known, make the system self starting. The capacitor 9 serves to suppress high frequency feedback oscillation.

The emitter-collector line of the fine control transistor 2 at the negative side of the network serves as a variable resistor serially connecting the drive coil with the source of power indicated and assuming transistor 1 as conductive. The base of transistor 2 is biased through the resistor 5, to a negative potential. In normal condition the transistor 2 is therefore completely modulated, and in its base-emitter circuit is at least part, if not all, of the drive coil 4 together with a diode 16 between the base and drive coil, but conductive counter to the base-emitter direction.

The normal or static working point on the characteristic curve of transistor 2 is predetermined by the resistance of the emitter-collector of transistor 1 plus, if necessary, a portion of the resistance of the coil 4, the resistance of the diode 6 in the conductive direction, and of course the biasing resistor 5.

By an appropriate selection of resistance of coil 4, the size of resistor 5 and the threshold voltage of the diode 6, the circuit can be so operative that upon an increase of the applied voltage, such as by a fresh battery, the transistor 2 becomes less biased to the conductive state.

In this manner the resistance emitter-collector line of the transistor 2 rises upon an increase in voltage across the coil 4 and the transistor 2 with the result that less current flows through the coil 4.

The various resistance values can be so chosen that under a predetermined applied voltage of, say, 1.2 volts the transistor 2 is completely modulated that is to say the input and output vary substantially linearly, while at voltages exceeding this amount the modulation becomes continuously less. For this reason the amount of drive current through the coil 4 continues to remain at the amount that 1.2 volts would cause to flow, even though a battery having a voltage, say, of 1.5 were connected to the shown terminals of the circuit.

This combination is so designed that upon an increase in amplitude of the oscillator above a predetermined amplitude, the voltage induced across the coil 4 by the movement of the associated permanent magnet exceeds the threshold value of the diode 6, so that the base potential of transistor 2 becomes increased in the sense shown by the arrow. For this dynamic stabilization the definitive values are the inductive action of the coil 4 the threshold value of diode 6 and the size of the resistor 5.

If the coil 4 is tapped in the mid portion so as to effectively include only a part 4" in the emitter-base circuit and leave the remainder 4' only as a driving part, the resistance of part 4 is to be considered for static stabilization, while for dynamic stabilization only the part 4" is to be considered for inducing voltage.

The diode 6 permits only such voltages of the proper 3 size to be'impressed in the base of transistor 2 that will enable proper functioning of the circuit using a transistor 2 of the p-n-p type.

If a n-p-n type transistor is to be used such as transistor 2' in FIG. 2 the polarity of the diode 6 is reversed as shown.

The diode 6 is preferably a silicon diode having a definite threshold voltage value.

I claim:

1. In a timepiece wherein a variable source of direct current is connected through a drive transistor to a drive coil for driving a permanent magnet on an oscillatory member tending to assume a null position, and wherein a pickup associated with the magnet times action of the drive transistor, the improvement comprising a second transistor to function as a variable resistor interposed between the drive coil and the source, a shunting line across the second transistor and at least a part of the drive coil, the shunting line serially containing a resistor and a unidirectional conductor, the base of the second transistor, the resistor and the unidirectional conductor being connected substantially directly together with one another in a common junction for varying the effective rea transistor to maintain a substantially uniform current flow through the drive coil when the drive transistor is conductive.

2. In a timepiece as claimed in claim 1, the terminal of the resistoropposite from said junction being connected substantially directly to a terminal ofthe source.

3. In a timepiece as claimed in claim 2, said terminal of the resistor being connected substantially directly to one of the output elements of the second transistor, whereby biasing control potential on the base'of the second transistor for a flow of current through the latter and through the drive coil is essentially proportioned to the value of said source of direct current.

References Cited UNITED STATES PATENTS 3,441,820 4/1969 Heermans 5823 RICHARD B. WILKINSON, Primary Examiner E. C. SIMMONS, Assistant Examiner US. Cl. X.R. 5828; 331183 

